Separation of materials of different specific gravities and media therefor



Patented Dec. 14, 1943 SEPARATION OF MATERIALS OF DIFFERENT SPECIFICGRAVITIES AND MEDIA THERE- FOR Charles W. Davis, Silver Spring, Md.,assignor to Chicago Development Company, Chicago, 111., a corporation ofIllinois No Drawing. Application July 17, 1939, Serial No. 2 8d ,88 7

8 Claims. (01. m sc) My invention is concerned with the separation ofgranular materials having difierent specific gravities and particularlyrelates to materials which have unusually satisfactory proper-- ties asmedia for such purposes.

In accordance with the prior art, heavy substances in a state of finedivision, have beensuspended in water so as to simulate a heavy liquidand the resulting suspensions have been used for the beneficiation ofsuch ores as those of zinc, coal, iron and the like. Among thesubstances employed for this purpose have been galena, magnetite,,andferro-silicon.. The use of each of these substances has definitedisadvantages which have militated against their more extended use. cultto recover since it is used in extremely finely divided form and,accordingly, its use has proven quite costly. Magnetite andferro-silicon, while relatively easily recoverable for reuse by means ofmagnetic separators, have a relatively low specific gravity which limitstheir use to a relatively few ores. These and other media which haveheretofore been employed offer other disadvantages with which thoseversed in the art are fully familiar and which require no elaboration.

In accordance with my present invention,

'media which can readily be converted into a state of fine division andare easily suspended in water inorder to simulate heavy liquids areproduced in a relatively simple and inexpensive manner. They may be madein a strongly ferromagnetic condition and possess'compa-ratively highspecific gravities, generally in the range from about 6.5 or somewhatless to about 8.2 or somewhat more. Their magnetic susceptibility andcoercive force may be varied from rather low values to those comparablewith iron or steel or with the best magnetic alloys. They may also beprepared in the form of solid lumps or in almost any state of divisiondown to the finest powder.

The primary advantages of the-media proso that the recovery of saidmedia for reuse byv means of magnetic separators may be readily andinexpensively accomplished.

The essential elements comprising the media of myinvention are lead or asource of lead such Thus, for example, galena is difli- Y as galena, andferro-magnetic material such as metallic iron, nickel, cobalt or theiroxides and alloys or the like. In certain cases, sulphur isa desirableconstituent.

The following examples are illustrative of the preparation of mediafalling within the scope of my invention. It will be understood'thatvarious changes may be made therein with respect to the proportions,temperatures and time of heating, and the like, without departing fromthe principles of my invention:

Example 1 Equal parts by weight of pulverized galena (200 mesh) andfinelycomminuted sponge iron (100 mesh) were mixed together and heatedat 750 degrees C. for 5 minutes in a closed crucible. The resultingproduct, of compact character, was

easily pulverized, 90% thereof being strongly *which had a specificgravity of 6.50, could be broken up easily into strongly magneticparticles.

coated with lead globules.

magnetic and 10% weakly magnetic. The specific gravity of the stronglymagnetic portion was 7.283 and said material was resistant to the actionof repeated Wetting and drying in air.

Example 2 2 parts by weight of pulverized galena (200 mesh) were mixedwith 1 part by weight of sponge iron (6 mesh) and the mixture was heatedat 650 degrees C. for 5 minutes. The magnetic portion consisted of 6mesh pieces The specific gravity of this material was 7.14.

Example 3 2 parts by weight of powdered galena and one part by weight ofpowdered iron were mixed together and heated at 500 degrees C. for 5minutes. product was strongly magnetic and had a specific gravity of8.12.

Example 4 2 parts by weight of finely divided galena (200 mesh) and 3parts by weight of magnetite mesh) were mixed together and heated at 800degrees C. for 5 minutes. The resulting product,

Example 5 A mixture of 8 parts by weight of powdered iron, 7 parts byweight of lead, and 1 part by weight of sulphur, were heated at 750degrees C. for 5 minutes. The resulting product was strongly magnetic.

Approximately 73% of the resulting Example 6 18 grams of sponge ironwere maintained for about 5 minutes incontact with 1000 cc. of a hotacid brine solution of lead sulphate whereupon metallic lead wasprecipitated on the surface of the iron. The acid brine solution of leadsulphate contained 14 grams per liter of lead as lead sulphate, 1.1grams per liter of sulphuric acid, and the solution was substantiallysaturated with sodium chloride. The lead-coated iron particles,comprising about 40% lead and about 60% iron, were removed from thesolution, dried, and heated in a closed crucible for about 5 minutes ata temperature of approximately 350 degrees C. The resulting materialpossessed a high magnetic susceptibility and was resistant to the actionof repeated wetting and drying in air.

In general, in its broader aspects, the invention comprises the heatingtogether, at suitably elevated temperatures, of lead or a lead compoundsuch as galena with any material having suitable magneticcharacteristics and appropriate specific gravity so that a heavymagnetic material results. In a more limited aspect of the invention, asdescribed in Example 6 hereinabove, the invention contemplates theutilization of any magnetic material which can have deposited upon itssurface a layer of lead and then be heated, particularly in the absenceof air, to produce a heavy magnetic material which is resistant to theaction of, or does not deteriorate by, repeated wettin and drying.

The proportions of ingredients comprising the media of my invention are,of course, subject to variation, as the examples hereinabove show. Iftoo little lead or galena is used, the resulting product is lessresistant to corrosion or repeated wetting and drying; and, if toolittle iron or other ferro-magnetic material is employed less of thefinal product is magnetic. Thus, for example, with equal parts by weightof lead and iron, 90% of the final product is strongly magnetic. Withtwo parts of lead to one part of iron, by weight, 73% of the finalproduct is strongly magnetic. With two parts of iron and 1 part of lead,by weight, about 99% of the final product is strongly magnetic. In thelight of these facts, those skilled in the art will be properly guidedin the practice of the invention.

The following examples are illustrative of the use of the media of myinvention for bringing about separations of the character describedhereinabove:

Example 7 A hematite iron, in which the gangue was a hard, siliciousmaterial,.was crushed to /2 inch' size. The heavy liquid" was preparedby mixing 100 mesh heavy magnetic material, produced as Example 8 Asilicious lead ore was treated generally as described in Example 7, theliquid suspension in thiscase being adjusted to an effective specificgravity of 2.7, the heavy magnetic material utilized being produced inaccordance with Example 4. The original ore, which contained 5% lead,was crushed to inch size. The concentrate assayed lead, the tails 0.72%lead, and the recovery was 92%.

Example 9 A zinc ore with dolomite gangue (5.4% zinc) was separated bymeans of an aqueous suspension of the product of Example 6, the heavymagnetic medium having a specific gravity of 8.2, and the aqueoussuspension being adjusted to an effective specific gravity of 2.9. Theconcentrate obtained assayed 60.8% zinc, the tailings 0.8% zinc, and therecovery was 86%.

What I claim as new and desire to protect by Letters Patent of theUnited States is:

1. A medium for the separation of granular materials of diiferentspecific gravities, comprising a magnetic material in finely dividedform and having a specific gravity of at least about 6.5, said magneticmaterial containing at least largely lead, iron and sulphur.

2. A medium for the separation of granular materials of differentspecific gravities, comprising a magnetic material in finely dividedform and having a specific gravity of at least about 6.5, said magneticmaterial containing at least largely magnetic iron oxide and a solidlead material.

3. A medium for the separation of granular materials of differentspecific gravities, comprising a magnetic material in finely dividedform and having a specific gravity of at least about 6.5, said magneticmaterial containing at least largely lead, a ferro-magnetic substanceand sulphur.

4. A process for the preparation of a medium for the separation ofgranular substances of different specific gravities, which comprisesmixing substantial amounts of galena and a magnetic material, heatingthe resulting mixture to a temperature between about 450 degrees C. andabout 1000 degrees C. and converting the medium to a finely dividedform.

5. The process of claim 4 wherein said magnetic material comprisessponge iron.

6. The process of claim 4 wherein said magnetic material comprises amagnetic oxide.

7. A process for the preparation of a medium for the separation ofgranular substances of different specific gravities, which comprisesmixing substantial proportions of a solid lead material, a 'magneticsubstance, and sulphur, heating'the resulting mixture to a. temperaturewithin the range of about 450 degrees C. to about 1000 degrees C. andconverting the medium to a finely divided form.

8. In the process of preparing a medium, in finely divided form, for theseparation of granular substances of different specific gravities fromeach other, the steps of contacting sponge iron with an acid brinesolution of lead sulphate whereby a substantial proportion of lead isdeposited on said sponge iron, and then heating the resultinglead-coated sponge iron to a temperature of at least about the meltingpoint of lead. CHARLES W. DAVIS.

